Subacromial Impingement Syndrome (SIS) and how it develops differs greatly between clinicians and paleopathologists. Clinical studies note that a particular type of scapular morphology (form) as being an important factor.This view is not shared by many anthropologists who insist that SIS is a result of altered biomechanics (function). This osteological study set out to determine whether the presence of a particular 'morphological package' was associated with SIS. A total of 62 adult human scapulae were selected from a Proto-Prehistoric New Zealand Polynesian Collection and from a Neolithic Thai Khok Phanom Di Collection. Subacromial lesions were identified by various observational techniques. Lesion thickness was then analysed with five variables including: percentage grading of surface degeneration, acromial margin shape, coracoacromial outlet shape, slope of the acromion and spine of the scapula. The findings of this study point to lesioned scapulae having a particular type of morphology rather than as a result of aberrant activity patterns developing this type of bony pathology.